1. Field of the Invention
The present invention relates to traffic signal systems, and is more particularly concerned with modifying control information forming frame signal programs, the control information being transmitted from a central station to intersection devices of the system, particularly of a street traffic signal system, for controlling signal generators belonging to the appertaining intersection devices, upon consultation of traffic information which may have been determined in the traffic areas whose traffic flow is controlled by the signal generators of the intersection devices.
2. Description of the Prior Art
A street traffic signal system is known from French Letters Pat. No. 1,481,270 which has a control central station and control devices connected thereto representing intersection devices, the control devices belonging to individual street intersections. The control devices are connected to traffic detectors with whose assistance the respective, current traffic situation is identified. The signals derived therefrom are then supplied to the central control station in order to change specific parameters of the signal schedules.
This, however, means that the individual control devices necessitate a correspondingly high circuit expense and that, moreover, justice cannot immediately be done to the respectively existing traffic conditions by means of an appropriate change of the signal schedules. On the contrary, under certain conditions, a relatively long time can be required in that the central control station is driven practically simultaneously by a multitude of control devices for a corresponding change of signal schedule.